含空洞地层中双线盾构施工引起的土体位移研究

SOIL DEFORMATION INDUCED BY DOUBLE TRACK SHIELD CONSTRUCTION IN GROUND STRATUM WITH CAVITIES

浅地层存在空洞是盾构施工导致土体位移过大的重要诱因之一。为有效计算土体位移,首先引入空洞收敛率,推导了空洞收敛变形造成的上部土体位移计算公式,再综合考虑双线盾构施工、空洞移动及收敛变形、正面附加推力、盾壳与土体摩擦力、附加注浆压力的影响,推导了含空洞地层中双线盾构施工引起的土体位移计算方法,结合算例对不同盾构施工因素、空洞半径、空洞中心埋深、空洞位置影响下的土体位移规律进行了研究。研究结果表明,引入不同盾构施工因素能更精确的计算开挖面前方的土体位移;接近先开挖侧隧道的空洞会对土体位移造成更大影响;接近空洞的地表沉降量随空洞埋深的增大而减小,远离空洞的地表沉降量随空洞埋深的增大而增大。

The existence of cavities in shallow stratum is one of the important inducements of excessive soil displacement caused by shield construction. To calculate the soil displacement effectively, the calculation formula of the upper soil displacement caused by the cavity convergence deformation is deduced with the cavity convergence rate. The calculation method of soil displacement caused by the double track shield construction in the stratum with cavities is deduced considering the effects of double track shield construction, cavity movement and convergence deformation, front additional thrust, friction between shield shell and soil, and additional grouting pressure. The soil displacement law under the influence of different shield construction factors, cavity radius, cavity center buried depth, and cavity position is studied through the examples. The results show that the soil displacement in front of the excavation face can be calculated more accurately by introducing different shield construction factors. The cavity close to the first excavated tunnel have a greater impact on the soil displacement. The surface settlement near the cavity decreases with the increase of the cavity buried depth, and the surface settlement away from the cavity increases with the increase of the cavity buried depth.